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A pointer is a data type which holds a memory address. While a variable accesses
that memory address directly, a pointer can be thought of as a reference to that
memory address.

To declare a pointer data type, add a carat prefix (

^

) before type. For example, if you

are creating a pointer to an 

integer

, you would write:

To access the data at the pointer’s memory location, you add a carat after the vari-
able name. For example, let’s declare variable p which points to 

word

, and then

assign the pointed memory location value 5:

dim p as ^word
'...

p^ = 5

A pointer can be assigned to another pointer. However, note that only address, not
value, is copied. Once you modify the data located at one pointer, the other pointer,
when dereferenced, also yields modified data.

The @ operator returns the address of a variable or routine, i.e.

@

constructs a

pointer to its operand. The following rules are applied to 

@

:

- If 

X

is a variable, 

@X

returns the address of 

X

. 

- If 

F

is a routine (a function or procedure), 

@F

returns F’s entry point (the result 

is of 

longint

). 

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- SOFTWARE AND HARDWARE SOLUTIONS FOR EMBEDDED WORLD

CHAPTER 5